Mars Lander Exposes More Ice

NASA's Phoenix Mars Lander's Robotic Arm comes into contact with a rock informally named "Alice" near the "Snow White" trench. This image was taken by the lander's Surface Stereo Imager on July 13.Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University

NASA's
Phoenix Mars Lander used its robotic arm to expose more of the hard icy layer
just below the Martian surface so that it can more easily gather a sample of
the material for analysis.

The trench,
informally called "Snow
White," was about 8 by 12 inches (20 by 30 centimeters) after digging
by the arm Saturday. Mission controllers sent commands to the spacecraft Monday
to further extend the length of the trench by about 6 inches (15 centimeters).

Scientists
said tests in a lab on Earth suggested more area must be exposed in order to
collect a proper sample.

"Right
now, there is not enough real estate of dark icy soil in the trench to do a
sample acquisition test and later a full-up acquisition" for the Thermal
and Evolved-Gas Analyzer (TEGA), said Ray Arvidson, Phoenix's "dig
czar," from Washington University in St. Louis. The TEGA instrument bakes
samples of the Martian dirt in tiny ovens and analyzes the vapors given off to
determine the composition of the regolith.

The plan to
gather a sample of the rock-hard ice involves using the robotic arm's rasp to
kick the icy soil into the scoop through a special capture mechanism.
Scientists also want to scoop up any loose material left in the trench after
the rasping activity, Arvidson said.

The rasp
has already been used to scrap the exposed icy layer, though those samples were
not analyzed. Samples of the shallower, non-icy soil from the Snow White trench
though have been examined by Phoenix's wet chemistry laboratory and optical
microscope.? Last week, the lander stuck
its fork-like probe into nearby dirt to see how well it conducts
electricity and heat.

"The Phoenix science team is working diligently to analyze the results of the tests from these
various instruments," said Phoenix principal investigator Peter Smith of
The University of Arizona. "The preliminary signatures we are seeing are
intriguing. Before we release results, we want to verify that our
interpretations are correct by conducting laboratory tests."

As the
robotic arm was extracting the fork probe from the soil on Saturday, it came
into contact with a rock called Alice near the trench. The arm is
programmed to stop moving when it encounters an obstacle.

Commands
sent to the lander Monday told it to move its arm away from the rock, dump out
soil that is in the scoop and extend the Snow White trench toward the lander.